<template>
  <div class="pagination">
    <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
    <button v-if="startNumAndEndNum.start > 1"  @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
    <button v-if="startNumAndEndNum.start > 1">···</button>

    <!-- 中间部分 -->
    <button v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page>=startNumAndEndNum.start" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{page}}</button>

    <button v-if="startNumAndEndNum.end <totalPage">···</button>
    <button v-if="startNumAndEndNum.end <totalPage"  @click="$emit('getPageNo',totalPage)" :class="{avtive:pageNo==totalPage}">{{totalPage}}</button>
    <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:['pageNo','pageSize','total','continues'],
  computed:{
    //计算总共多少页
    totalPage(){
      return Math.ceil(this.total/this.pageSize);
    },
    //计算出连续的页码的起始数组与结束数字
    startNumAndEndNum(){
      //定义两个变量用于存储起始数字与结束数字
      let start = 0, end = 0;
      //连续页面数字5【就是至少五页】，如果出现不正常的现象【就是不够五页】
      if(this.continues>this.totalPage){
        //总页数小于连续的页码数
        start = 1;
        end = this.totalPage;
      }else {
        //正常
        start = this.pageNo-Math.floor(this.continues/2);
        end = this.pageNo+Math.floor(this.continues/2);
        //排除start出现-1和0的情况
        if(start < 1){
          start = 1;
          end = this.continues;
        }
        //排除end出现比总页码还大的情况
        if(end>this.totalPage){
          start = this.totalPage - this.continues + 1
          end = this.totalPage;
        }
      }
      return {start , end};
    }
  }
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: rgb(200,22,35);
      color: #fff;
    }
  }
}
</style>
